1. Field of the Invention
This invention relates to an improved dental remedy which is used for vital pulp covering and root canal filling, and the preparation method therefor.
2. State of the Prior Art
The inventor of this application has made eager and extensive studies in the technical field concerned for many years. The outcomes of the studies have been disclosed in the patent specifications of Japanese Patent Publication Nos. Sho. 29-8197/1954 (Patent No. 212,303), Sho. 45-39834/1970 (Patent No. 637,507), Sho. 46-4757/1971 (Patent No. 621,124) and Sho. 50-5513/1975.
In brief, the method for preparing the dental remedy disclosed in the above patent specifications comprises the steps of: reacting formaldehyde and phenol compounds such as guaiacol with the addition of an alcohol-soluble vegetable oil or an interesterification product of a vegetable oil and a polyhydric alcohol to obtain an oily, millet jelly-like intermediate condensate; separating and rinsing the oily product (thus obtained product will be hereinafter referred to simply as "intermediate condensate"); and immediately before use, kneading the intermediate condensate by adding the powder of pure calcium hydroxide or calcium oxide and a smaller amount of x-ray contrast medium.
Several disadvantages caused in the conventional method have been obviated by degrees in the methods as disclosed in the foregoing patent specifications, however, they are not yet complete. That is, when the refined intermediate condensate obtained through the above method is kneaded with the powder mainly containing calcium hydroxide or calcium oxide and the kneaded mixture is used for treatment, it is subject to slight coloration after the lapse of long period of time. Though the dental remedy is more desirable as compared with the conventional ones, it is still slightly irritable, which property is clinically acceptable but somewhat defective in view of pathological results.
Further, in the method as disclosed in Japanese Patent Publication No. Sho. 50-5513/1975, the tendency for kneaded material to cure too rapidly has been eliminated by kneading the intermediate condensate with the powder mainly containing calcium oxide. By replacing calcium hydroxide with calcium oxide, the pot life of the kneaded material before curing can be made long and proper, for example, 20 to 30 minutes. However, the defect for the filled material to color after the lapse of a long time has not yet been removed.